I5 Head Porting and Polishing

[JShadzi at aol.com]

<< Hi all,

 i am going to start rebuilding one of the I5 heads i have lying round and
 need some adice pleae on how to port and polish. As i have never done this
 before i need to know what tools i need and how to do it. I have the Dremel
 and decent power drill but don't know what type of grinding stones to buy,
 and of course where to remove metal and where not too.>>

As far as porting goes, a good site is www.standardabrasives.com, they have a
write-up on general porting, and also sell some good kits to get you started
(highly recommended).

The best thing to do if you don't have a flow bench is to do a basic polish
and port match, go in a smooth all the ports to an 80 grit finish, match the
IM and EM ports to the head.  Don't remove too much material, just smooth
every surface that you can.  Try to remove material from the sides of the
snub around the valve guide, and pay special attention to the
"short-side-radius", where the port turns down into the valve, try to smooth
it and reduce the harshness at which it transitions.

Don't use grinding stones on alum, try sanding rolls, they work great, are
cheap, and can really get in the tight spots.  I doubt you can do much with a
Dremel, probably use your drill, though it could spin faster, about 10k RPM
is perfect for porting.  You shouldn't really need any carbide bits, keep it
simple and slow with the sanding rolls.

Another great trick, take a piece of 1/4" steel rod, about 8" long, and cut a
very small  slot (like a hack saw blade) in the top 1" long.  Now you can
take 1" sand paper strips and wrap them around the rod, makes a great flapper
wheel or sanding roll, you just keep ripping off the end as the sandpaper
wears...my best porting tool.

With this tool you can port the intake manifold too, only the lower runner
portions however, which usually need it anyway with 1/8" of caked on oil in
the runner, just grind it all out and smooth it, then match it to the ports
on the head using the IM gasket as a guide.


<< On a slightly different subject, I also plan to install larger valves, what
 size should I go to??? The engine is a 2226cc KV engine (out of a UK Coupe
 Quattro). Am i biting off more than i chew???
  >>

The 40mm valve is a great upgrade in NA cars, I also have 40mm valves in my
80tq, the motor breathes very well.  Use the 40mm valve out of the NG cars,
it will require a bigger seat, won't fit in the 38mm seat, but that is where
the real flow gain is anyway.

Also, on NA cars, you can have 1.5mm machined out of the ID of the valve seat
which effectively gives you a bigger valve, but since it removes valve seat
area, it is not recommended for a turbo motor where valve cooling is
important.

You are not biting anything off, this is all pretty standard stuff...now,
moving the ports up to make them straighter, and relocating the sparkplug to
optimise flame propogation...that could be a big bite.

HTH,

Javad
80tq.com